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Cortical plasticity: it's time to get excited about inhibition
August 24, 2006Brandeis research sheds new light on neural circuits
Waltham, MA-Research from Brandeis University published online this week in Nature offers new insight into how neural circuits are shaped by experience. The article provides new evidence for the mechanisms that affect the ability of the visual cortex to plastically rearrange itself following periods of visual deprivation.
"Getting our brains to wire up properly requires experience during an early critical period of development, and understanding the mechanisms of this experience-dependent plasticity is critical for understanding human development, its disorders, and for designing strategies that promote optimal cognitive development during early childhood," explained author and neuroscientist Gina Turrigiano.
Neuroscientists have long known that the brain needs proper sensory stimulation to develop correctly and that experience can induce plastical changes in the functional architecture of sensory cortices. Animals that grow up with one eye covered during a critical period of brain development lose some of their visual acuity and ability to respond to certain visual stimuli. In these experimental conditions, Turrigiano and colleagues explored the visual cortex circuit of young rats by recording electrical activity of neurons and their connections.
"We have found an important and novel mechanism involved in the loss of function of cortical circuits," said co-author neurophysiologist Arianna Maffei. "While our results directly apply to the loss of visual function secondary to sensory deprivation, they very likely represent a more general strategy for cortical networks to respond to experience."
The researchers showed that the lasting cortical shut-down induced by visual deprivation at early stages of development is the result of a massive increase of cortical inhibition. Specifically, the strength of inhibitory synaptic connections between two types of neurons in the layer receiving the input - the inhibitory fast-spiking basket cells and the excitatory star pyramidal neurons - increased 3-fold.
While it has been historically believed that regulation of excitatory synapses is most critical to the development of neuronal circuitry, and that loss of function is the result of a depression of excitation, this research demonstrates that inhibitory synapses play a critical role in proper network wiring and ultimately in preserving - or disrupting-neuronal function.
"Our data suggest a major revision of thinking about how experience works on our brains," noted Turrigiano. "Instead of targeting exclusively excitatory networks, a major locus of plasticity lies within the inhibitory networks. Our data show that inhibitory networks within the cortex are highly plastic, and that some pathological states arise through inappropriate activation of inhibitory plasticity."
Brandeis University
"We have found an important and novel mechanism involved in the loss of function of cortical circuits," said co-author neurophysiologist Arianna Maffei. "While our results directly apply to the loss of visual function secondary to sensory deprivation, they very likely represent a more general strategy for cortical networks to respond to experience."
The researchers showed that the lasting cortical shut-down induced by visual deprivation at early stages of development is the result of a massive increase of cortical inhibition. Specifically, the strength of inhibitory synaptic connections between two types of neurons in the layer receiving the input - the inhibitory fast-spiking basket cells and the excitatory star pyramidal neurons - increased 3-fold.
While it has been historically believed that regulation of excitatory synapses is most critical to the development of neuronal circuitry, and that loss of function is the result of a depression of excitation, this research demonstrates that inhibitory synapses play a critical role in proper network wiring and ultimately in preserving - or disrupting-neuronal function.
"Our data suggest a major revision of thinking about how experience works on our brains," noted Turrigiano. "Instead of targeting exclusively excitatory networks, a major locus of plasticity lies within the inhibitory networks. Our data show that inhibitory networks within the cortex are highly plastic, and that some pathological states arise through inappropriate activation of inhibitory plasticity."
Brandeis University
Visual Cortex Current Events and Visual Cortex News RSSClues to visual variant Alzheimer's; myopia and diabetic retinopathy risk
Two studies are of particular note in today's Scientific Program of the 2009 Joint Meeting of the American Academy of Ophthalmology (AAO) and the Pan-American Association of Ophthalmology (PAAO): a report by Swiss neuro-ophthalmic researchers about vision exam clues that should make ophthalmologists suspect an atypical variant of Alzheimer's disease; and new evidence from a Singapore National Eye Center study that diabetics who are nearsighted may be less susceptible to diabetic retinopathy.
Treating ROP in tiny preemies; better glaucoma follow-up in urban clinic
Highlights of today's Scientific Program of the 2009 American Academy of Ophthalmology (AAO) - Pan-American Association of Ophthalmology (PAAO) Joint Meeting include: John T. Flynn, MD, Columbia University School of Medicine, discussing the ever-tougher challenges Eye M.D.s face in caring for the vision of the tiniest premature babies; and a report by Bradford W. Lee, MD, Stanford University School of Medicine, on barriers to glaucoma follow-up as perceived by patients in an urban, culturally diverse clinic.
Can we 'learn to see?': Study shows perception of invisible stimuli improves with training
Although we assume we can see everything in our field of vision, the brain actually picks and chooses the stimuli that come into our consciousness.
Scans show learning 'sculpts' the brain's connections
Spontaneous brain activity formerly thought to be "white noise" measurably changes after a person learns a new task, researchers at Washington University School of Medicine in St. Louis and the University of Chieti, Italy, have shown.
Babies see it coming
Do infants only start to crawl once they are physically able to see danger coming? Or is it that because they are more mobile, they develop the ability to sense looming danger?
Perceptual learning relies on local motion signals to learn global motion
Researchers have long known of the brain's ability to learn based on visual motion input, and a recent study has uncovered more insight into where the learning occurs.
Study Finds Needle Biopsies Safe in 'Eloquent' Areas of Brain
After a review of 284 cases, specialists at the Brain Tumor Center at the University of Cincinnati (UC) Neuroscience Institute have concluded that performing a stereotactic needle biopsy in an area of the brain associated with language or other important functions carries no greater risk than a similar biopsy in a less critical area of the brain.
MIT: Long-distance brain waves focus attention
Just as our world buzzes with distractions - from phone calls to e-mails to tweets - the neurons in our brain are bombarded with messages.
'Singing brains' offers epilepsy and schizophrenia clues
Studying the way a person's brain 'sings' could improve our understanding of conditions such as epilepsy and schizophrenia and help develop better treatments.
Preclinical work shows how one gene causes severe mental retardation
Researchers at Duke University Medical Center and the University of North Carolina have discovered in mice how a single disrupted gene can cause a form of severe mental retardation known as Angelman syndrome.
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